Bare Knuckle Pickups Forum
Forum Ringside => Tech => Topic started by: gordiji on July 22, 2010, 09:45:09 PM
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I've just rebiased my engl screamer (breaking my rebiasing 'virginity').I used a probe and with the trim pot at full
adjustment i got 37.8ma. I chickened out of measuring the grid plate voltage and assumed an average of 450
courtesy of the eurotubes website.They recommend a current draw range of 38- 42ma with this amp.
Does a low reading mean i'm biased to the cold side? I would have been happier if i could have set it in the middle of the range.
The engl tubes i removed where interestingly set at the other extreme trim pot setting , i replaced them with jj's because the engl's are pricey and was interested in any difference( i replaced all the pre amp tubes too)
Having played a good bit today, it sounds great.The clean isn't as sparkly but still lovely and the crunch and overdrive are noticibly warmer, i get pretty much the same sound but the eq settings differ with the newies.
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Any engineer will tell you 37.8 mA is 38 mA, and is certain close enough for rock and roll.
I doubt whether you will hear any difference between 38 mA and 42 mA.
Biasing an amp too cold will result in excessive crossover distortion, which I think it is safe to say, is regarded to sound terrible. Certainly my experiences would concur with this view.
However, biasing an amp too cold is perfectly safe.
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thanks jpf.